Spray gun



Aug. 21, 1956 A. c. HOPKINS SPRAY GUN Filed DSC. l5, 1954 INVENTOR.

ARTHUR C HOPKINS Arron/usr Y United States Patent `SPRAYGILJN Arthur C. Hopkins, Carthage, N. Application December 115, 1954,;Serial No."4*1554631` 6 Claims. v-(Cl. l299140) The present invention relates .to `spray guns, particu- .larlyfor spraying paint, vlacquer .and .similar liquids. v

vvIn the conventional spray gun, .the air is mixed with the paint .or lacquer outside .the paint .or lacquer nozzle. 'Thelacquer or paint .is `discharged from its .nozzleunder .about eight pounds pressure and air underforty .pounds .pressure .or so hits the liquid toatomize .the liquid, `and to drive the liquid on out ofthe nozzle of the .gun .and to carry the atomized liquid on to the object being painted. `It has been found, however, that .the .high velocity ,or .pressure ofthe air dries the 4atomized droplets of paint or lacquer, so .that forty .to fifty percent of the.paint .or .lacquer is actually .dried and lost before .it reaches .the object .being-coated.

In i the vconventional .spray .-gun, moreover, conventional .conical valves are provided to control thellow of .airand of paint or lacquer, andgaskets or washers are .usedto .insure proper .seating of these valves. 'Tl-he `gaskets or washers tend to deteriorate -very rapidly, however, 'because of the solventin thelacquer or, paint.

In the conventional spray gun, furthermore, 'lacquer .or .paint is .leftiin the nozzle, after 4the gun lis shut off, which dries inthenozzle ,thus tending to clog the gun.

One ^object .of .the present linvention .is to provide a :spray: gun which will-be more efficient in the use lo'f paint orlacquer, or the like. "To this end "it is anaim .of the invention to .provide a spray -gun in which the `paint or lacquer can `be supplied to the mixing chamber under ..1owpressure, and no high air 4pressure will have `to`be .used .to ratomize lthe liquid.

Another object of .the invention is to,prov`id-ea .spray `.gun'in-which thecompressedair is supplied in such way as simultaneously to atomize the Lliquid. coating material and .to driveit forward .to theobject to be coated.

Another vobject of the invention is Lto l.provide a spray gun .of the-character described in which .theair-operate's ..to.automa'ticlly clean paint outof the Vgun whenthe .paint'ow is stopped, and toclean the Egun again be'lfore i'thepintiiowis started. l

Another object of the invention Vis to provide .an 4im- ,.proved s praygun which is yso constructed that 'the air will-.come on before the paint starts 'to ow, Land'will .remain on a'fter the paint iiow is stopped lthus insuring againsnpaint drying in the nozzleand clogging the gun.

Another object of the invention is to providetaspray gun'having an improved type of .valve which will Seat very tightly and which will be unaffected "bytsolvents "in 'the paint or lacquer, and which hasallife as long as'the llife ofthegun` itself.

`O'ther objects .of 4the inventionis to.simplify"tl1'estruc 'ture of a sprayfgun, so that it'will not only be inexpensive in constructionbut will be more eihcient linuse,positive 1in operation, uniform inaction, easily controlled, "and unlikely to .get vout of order.

'Other .objects oflthe invention willbe apparentiherenafter from Kthe specification 'and from `'the recital of "the appended claims.

"ice

In the drawing:

Fig. :v1is `a'partrsection, `part side elevation, of a spray ...gun :constructed :according to one embodiment of this invention;

Fig..2.fis :a .fragmentary pian view of this gun;

Fig. r3 is `a=part1planview, part section of this gun;

Fig. 4 is a .transverse .section `through the gun taken substantially ion .the line 4-4 lof Fig. 1, looking inthe direction of the arrows;

Fig..5:is.afragmentary sectionshowing a modifedform of :nozzle for the gun;

.'Fig. zisa frontview Vof ythe nozzle shown in Fig. 5;

.Fig/7 is fa 'fragmentary section showing a still 'further :form fof nozzle; and

Fig. .Sfis a vfrontviewof the nozzle .of Fig. 7.

Referring now'to the drawings andiirstto Figs. 1 to 4 inclusive, 10 denotes the `body portion or barrel of the `spray gun. 'The lbody portion or barrel 10 is 4recessed :at-its:topnasindicated.at 1'1 in Fig. 4, and has ahardened, .superfnished metal'plate 12 fastened tin the recess. vSlid- .fably mountedfonthe plate :12;is another'hardened, superanished, nnetal yplate 14. The .two .plates 12 yand 14 lconstitute together the lcontrol :valve of the spray gun, as will appear hereinafter. Plate 14 is the movable .(slidtable.) elementfof sthisvalve. It is connected by azpin 15 (.Figs. :.1 Yand 3) `with the front zfurcated endi16 .of .a link ..17. This .link :1'7 is pivotally connected :at Tits .f1-ear end vby -means -iof 1pin :18 .to therockable .operatingeven =or trigger, 20fzof-.the gun.

The .body portion'or'barrel 10 of the gun has a hand :oripistolgrip 26 .riveted orzotherwise secured to it vat its lreartend. This handiorpistol grip includes the '.twospaced plates (22, The .trigger 20 is pivotally mounted .between these pplates .by pin 24. The link 17 travels .in the :space between :these plates. The movement .of vthe 'trigger 20 is limited by an adjustable stop screw 25 that threads into fa -solid vintermediate block .portion of the hand grip 26. By adjusting this screw :the =flow ofthe 4iluicLfmay be-regulated from nothing tofulliport opening .as will be Aclear hereinafter. A leaf spring 27, `that `is fastened at `one end by means of screw 28 :to the .hand rgrip, andthatcarries 4a roller 29 at -its-other end, serves vtoresilientlypress the trigger 20 counterclockwise about :its pivot 24, .to urge rvalve member `14 constantly .toward .closedgp'osition The leaf spring 27 fulcrums on a screw .3.0 thatisfadjustably threaded Ainto the hand grip.

The lacquer, or paint, or other :coating liquid is Vsup- ;.pliedlo the gun from a hose through ducts 40 and v41 .(Fig. 4) ein :the body jportion -10 of the gun. Duct `41 communicates with a rear 'hole 42 that .extends through @late 12. This=hole is adapted, vin turn, tocommunicate -with .-anelongate groove 43 inthe bottom surface ofthe ,plate :14.

The 'plate A12 vhas Vanother hole 44 .in it adjacent its front end which also communicates with igroove 43 lin plate 114, v,thereby connecting holes '42 and 44, .when plate 14 is pulled'to the left as shown vin Fig. l. fl'he *.hodyportion 10-has a duct 44 init, which communicates with hole l44and ywhich extends first downwardly, then fiorwardlyandoutwardly, as shown in Fig. 3. The duct \4`4 comrnunicates at its front-end `with an angular duct 11451which supplies Ithelacquer or paint to a chamber 46 :formed in'ba'rrel 10. 'Chamber 46 ,surrounds an air jet -47 that:is"threaded.into the body portion orbarrel 10.

Afremovablenozzle 48 is threaded onthe frontend of Lthefbody portion or barrel 10. This nozzle 48 has a conifca'l or spherical seating'portion 49 Vwhich seats in a-cor- -respondinglyshaped seat formed on the front end yof the 0 bore146'offbodyportion'or barrel 10. `Seating portion49 which tits tightly in the bore or chamber 46 of the body 10. The sleeve portion of the nozzle has a forwardly tapering conical bore S1 which surrounds the conical tip 52 of air jet 47 and which has substantially the same cone angle as the outside surface 52 of the air jet.

The bore 51 communicates with the discharge chamber 57 of the nozzle. Mounted in the chamber 57 to extend transversely of one another are two pins and 56. The nozzle has a collar portion 54, which surrounds its sleeve portion 50, and which is spaced radially from the sleeve portion. This collar portion is internally threaded and externally knurled so that it can readily be threaded on the body portion or barrel 10 of the gun.

An airline for compressed air is connected to a duct (Fig. 4), similar to duct 40. This duct in turn leads into a right angular duct 61, similar to duct 41, which in turn leads into a hole 62 in the plate 12. This hole communicates with a longitudinal groove 63 in the underface of the plate 14, parallel to and similar to groove 43. In the plate 12, adjacent its forward end, is another hole 64, which is adapted also to comunicate with groove 63 when plate 14 is in the position shown in Fig. 1. In the body portion 10 of the gun there is a duct 64', similar to duct 44. This duct communicates with a duct 65 (Figs. 3 and 7), which extends inwardly of the body portion of the gun, and which communicates with a duct 66 that extends axially, centrally through the air jet or nozzle 47.

The compressed air flowing through the duct 66 atomizes the coating liquid and forces the lacquer or paint ahead of it out of the reduced diameter mouth of the chamber 46 into chamber 57, where it is further broken up by pins 55 and 56, and whence it is sprayed in a pattern controlled by the shape of the mouth of the chamber 57 on the wall or other object to be coated. The baffles 55 and 56 keep the air turbulent even though the air is slowed down after it leaves the air jet. This prevents the fluid from solidifying in the nozzle.

One of the features of the gun of the present invention is the sliding plate valve 14--12- Unlike the valves used in conventional spray guns, the plates 14 and 12 do not require any gasket or washer between them. The upper surface of the plate 12 is supernished and ilat; and the opposed, lower surface of the plate 14 is also super-finished and fiat. Due to the super-finish, the two plates have frictional adherence with one another so that they cannot be lifted apart, although they can be slid on one another. They provide, therefore, an excellent seal. No leakage can occur, therefore, between them. They are held in engagement, however, by a pressure roller (Figs. l and 2) carried by a yoke 71 which is supported on the free end of a leaf spring 72. This leaf spring is mounted on a pin or stud 73 which is secured 4in or integral with an arm 74 that extends laterally and upwardly from a boss 75, which is formed on the upper face of the gun portion 10. A knurled shoulder screw 76, which engages the leaf spring 72 and which passes therethrough to thread into the boss 75, is provided to adjust the pressure of the leaf spring 72.

The valve 14-12 operates by sliding movement of the plate 14. The valve is opened when the plate 14 is pulled to the left as shown in Fig. l. By releasing the trigger 20 it is returned to normal, closed position by spring 27 operating through trigger 20. When the plate 14 is pulled to the left by operation of the trigger 20, the groove 43 in the plate 14 is brought into registry with the ports 42 and 44 in plate 12, and the groove 63 in plate 14 is brought into registry with ports 62 and 64 in plate 12. This permits the coating liquid and the compresed air to ow into the chamber 46 and into the jet duct 66, respectively. The paint or lacquer can be supplied to the chamber 46 under low pressure. It is expelled from the gun by the pressure of the compressed air flowing out of the duct 66. In conventional guns, the mixing of the air with the paint or lacquer occurs outside the paint nozzle or jet. This requires greater air pressure because the air does not drive the paint or lacquer to the surface being coated but only atomizes it. In the gun of the present invention the air drives the lacquer or paint, as well as atomizes it.

When the trigger 20 is released, the spring 27 returns the plate 14 to the right, and the solid portion of plate 14 covers ports 42 and 62 of plate 12, thereby closing off the ports 42 and 62 from communication with grooves 43 and 63, and stopping flow of both the coating medium and the compressed air. The forward, return movement of the block 14 under actuation of the spring 27, when the trigger 20 is released, is stopped by a stop pin 33 (Figs. 1 and 2) which is secured in the body portion 10.

It will be noted that the groove 63 in the plate 14 for the air line is longer than the groove 43 for the paint or lacquer. This insures that groove 63 will register with port 62 before groove 43 registers with port 42, and that groove 63 will remain in registry with port 62 after groove 43 has moved out of registry with port 42 and the solid portion of plate 14 has covered port 42. Thus, the air will come on before the paint starts to ow, when the trigger is pressed to pull the plate 14 to the left in Fig. l; and the air will remain on after the paint ow is stopped, when the trigger is released. Thus the nozzle 48 will be cleaned out by air before the paint or lacquer starts to ow, and will be cleaned out again by air after the paint or lacquer is shut off. This insures against paint or lacquer drying in the nozzle and clogging the gun.

In the conventional gun forty to fifty percent of the paint or lacquer is lost because, due to the high air pressure, the droplets dry before they hit the surface being coated. Applicants gun eliminates the high pressures, andinsures maximum eiciency in use of the paint or lacquer: Screws 67 and 68 which thread into the gun portion 10 at the junctures, respectively, of the ducts 40 and 41 and of the ducts 60 and 61, serve as throttle valves controlling the amount of liquid and air, respectively, flowing into the gun.

In the conventional gun, the gasket or washer used for the control valve deteriorates very rapidly because of the solvent in the lacquer and paint. There is no such possible deterioration of the sliding block 14 of the present gun, which acts as the control valve. This block, and the block 12 can be made, for instance, of tungsten carbide, or any hard material, which can be super-finished, and which is resistant to wear.

Various forms of nozzles may be employed in the gun of the present invention. One form of nozzle is shown in Figs. 1, 2 and 3. Here chamber 57 has a circular mouth and delivers the atomized coating material in a circular spray.

Another form of nozzle is shown in Figs. 5 and 6. Here the air jet 47 may be similar to the air jet 47 described in the rst embodiment of the invention, but the nozzle itself is made in two pieces, one piece 48' setting into the forward end of the sleeve-like gun portion 10 and having a forwardly tapering conical bore 51 similar to the bore 51 of nozzle 48. Here the nozzle is provided, however, with a flange portion and there is a separate knurled ring nut 81 which engages over this ange portion and threads onto the forward end of the tubular gun portion 10 to hold the nozzle in place on the gun. Nozzle 48' has also a somewhat longer forwardly tapering, conical bore 51 than bore 51 of nozzle 48; and chamber 57 of nozzle 48 has also a somewhat longer rearwardly tapering rear portion joining bore 51' to deline a narrow mouth between the two bores. Pins 55 and 56 are provided in the nozzle 48', as in the first described embodiment of the invention, for the purpose of creating turbulence in the atomized paint or lacquer to insure uniformity of distribution of the paint or lacquer over the surface being painted. The nozzle of Fig. 5 has the advantage over the nozzle of Fig. 3 that the nozzle Portion 48' can be adjusted at any angle about its axis, as

required in order to insure proper-p1aing fo'f't'the lpaint upon the surface, being painted. i

Another form of nozzle that maybe use"d""on'the gun of the present invention is iliustrated'tin Figs. "7a'11dl8. Here the air jet 47 threads intothebodyportionilll of the `gun as in the previous'embodiments, ibut'is atted off at its front end and has a'restricted'mouth, denotedat 86 formed at the convergence of a`re'cess itin thefront face of the air jet and of a bluntly"tap'eredfportion'at'the front end of the duct 66". Here the'airijetexten'ds 'completeiy through the tapered bore '1"-of 'the nozzlepiece 48, leaving but a very narrow annular "space ,around it between the nozzle piece and the air jet. With'this nozzle the paint is mixed with the Vair Tin `the enlarged chamber 57" formed in the nozzlepie'ce "48"; 'andit'lislin this chamber 57 that atomizing occurs. .This 'chamber `57'is considerably enlarged 'as compared'with thefchambers 57 and 57', respectively, 'of thenozzle's'slrown Vin vFigs. 3 and 5. The small angles atftheiinsideand 'out- -side of the mouth of the air jet 447 te'nd'to"explode"the of the invention shown'inFigs. 3 and 6 'the mouth of the nozzle is round.

in conventional 'guns approximately Viive thousand cubic inches of airareiused for each cubic inch-of lluid. In the gun of the present invention the air is mixed with the lacquer or paint inside the gun. Therefore, low pressure can be used on the paint,iincreasing the e'ciency of the gun, and reducing loss ofpaint'orilacquerseventyfive ,percent or more.

While the invention has been described in connection with several different embodiments thereof, it will be understood that it is capable of further modication; and this application is intended to cover any variations, uses, or adaptations of the invention following, in general, the principles of the invention and including such departures from the present disclosure as come within known or customary practice in the art to which the invention pertains, and as may be applied to the essential features hereinbefore set forth and as fall within the scope of the invention or the limits of the appended claims.

Having thus described my invention, what I claim is:

l. A spray gun comprisingy a barrel, a discharge nozzle mounted on the forward end of said barrel, an axiallybored jet nozzle mounted in said barrel and communicating with said discharge nozzle, said barrel and discharge nozzle having a conjoint bore, said jet nozzle having a stem of less diameter than the diameter of said bore whereby to provide a chamber between said jet nozzle and said bore, a liquid conduit for supplying liquid to said chamber, a second conduit for supplying a compressed gas to said jet nozzle, and a single valve for controlling the supply both of said liquid to said liquid conduit and of the compressed gas to said second conduit, said valve comprising a pair of plates, one of which has two pairs of ports therein, one port of one pair of ports communicating with said liquid conduit and the other port of said one pair of ports communicating with the source of supply of the liquid, one port of the other pair of ports communicating with said second conduit and the other port of said other pair of ports communicating with the source of supply of the compressed gas, the other of said plates having a pair of grooves therein, one of which registers, respectively, with the first-named pair of ports when said valve is open and the other of which registers with the other pair of ports when said valve is open, one of said plates being reciprocable on the other, and when moved in one direction opening said Valve, and

,essere when moved inthe 'opposite direction closing said valve, and means for reciprocating said reciprocable plate.

'-2. VAspray 'gun'comprising 4abarrel, a 'dis'charge'nozzle mountedon `the forward end 'of said barrel, an v'axiallybored jet nozzle "mounted in said barrel VVand communicatin'gwithsaddischarge nozzle, said barreland'discharge nozzl'e having 'a' conjoint bore, said jet nozzle ihaving'a stemo'fless diameterthan the diameter "of 'said 'bore whereby toprovide a chamber between sai'd'jet nozzle'andsaidlbore, a liquid conduit forv supplying'liquid to saidchamberfasecond conduit for supplying `a'cornp'ressed 'gasto'saidljettnozzle and `a single valve forc'ontrolling`the`supply`both dfsaid liquid'to said liquid 'conduit 'and'ofthe compressed gas to said second conduit, sai'dvalve comprisinga'jpair ofplates, 'one of which has two kpairs ofports therein, -one'port of'one pair of'ports `communicating with said liquid conduit and the other port `of"s'aid one'pairfpor'ts communicating withthe source o'fsupply f'the liquidyoneport ofthe other pair of ports .'co'rnmunicating'with said second conduit and theother 'portof said Aother pair vof p'orts communicating with 'the source 'of supply 'o'f 'the :compressed gas,`the other of 'said plates having ajpair of grooves therein, one of which registers with and 'connectsboth of said one pair ofports whensaid'valve i's open and the other of which registers with and connects .both of said other pair of ports when said valve`is open,'said other plate being reciprocably sli'dalble'on Vsaid one plate and being moveable in one direction to'open said valve and in the opposite direction to close said valve, the second-named groove of said other plate 'being longer than the first-named groove thereof, whereby the compressed air supplyis-turned on before, and shut olvafter, the liquid supply.

3. A spray gun'having a nozzle, a liquid conduit .for

` supplying liquid lto said nozzle, a gas conduit vfor supplying compressed gas to said nozzle to atoinize theiliquid, and asingle valve 'for controlling the supply Vboth of 'theliquid and of the compressed gas to said nozzle, said valve comprising a pair of plates, one of which has two pairs of ports therein, one port of one pair of ports communicating with said l-iquid conduit and the other port of said one pair of ports communicating with the source of supply of the liquid, one port of the other pair or" ports communicating with said second conduit and the f other port of said other pair of ports communicating with a source of supply of the compressed gas, the other of said plates having a pair of grooves therein, one of which registers, respectively, with the first-named pair of ports when said valve is open and the other of which registers with the other pair of ports when said valve is open, one of said plates being reciprocable on the other, and when moved in one direction opening said valve, and when moved in the opposite direction closing said valve, and means for reciprocating said reciprocable plate.

4. A spray gun having a nozzle, a liquid conduit for supplying liquid to said nozzle, a gas conduit for supplying compressed gas to said nozzle to atomize the liquid, and a single valve for controlling the supply both of the liquid and of the compressed gas to said nozzle, said Valve compris-ing a pair of plates, one of which has two pairs of ports therein, one port of one pair of ports communicating with said liquid conduit and the other port of said one pair of ports communicating with the source of supply of the liquid, one port of the other pair of ports communicating with said second conduit and the other port of said other pair of ports communicating with the source of supply of the compressed gas, the other of said plates having a pair of grooves therein, one of which registers with and connects both of said one pair of ports when said Valve is open and the other of which registers with and connects both of said other pair of ports when said valve is open, said other plate being reciprocably slidable on said one plate and being movable in one direction to open said valve and in the opposite direction to close said valve, the second-named groove of said other plate being longer than the firstnamed groove thereof, whereby the compressed air supply is turned on before, and shut oi after, the liquid supply.

5. A spray gun comprising a barrel, a discharge nozzle mounted on the forward end of said barrel, said barrel and discharge nozzle having a conjoint bore which along part of its length has a forwardly converging taper, an axially bored jet nozzle mounted in said bore and having its front end disposed rearwardly at a distance from the front end of the tapered part of sa-id bore, said jet nozzle having a stem of less diameter than said bore, whereby to provide a chamber between said jet nozzle and said bore, a liquid conduit for supplying a compressed gas to said jet nozzle, and a single valve for controlling the supply both of said liquid to said liquid conduit and of the compressed gas to said gas conduit, said valve comprising a pair of plates, one of which has two pairs of ports therein, one port of one pair of ports communicating with said liquid conduit and the other port of said one pair of ports communicating with the source of supply of the liquid, one port of the other pair of ports communicating with said second conduit and the other port of said other pair of ports communicating with the source of supply of the compressed gas, the other of said plates having a pair of grooves therein, one of which registers with and connects both of said one pair of ports when said valve is open and the other of which registers with and connects both of sa-id other pair of ports when said valve is open, said other plate being reciprocably slidable on said one plate and being movable in one direction to open said valve and -in the opposite direction to close said valve, the second-named groove of said other plate being longer than the rst-named groove thereof, whereby the compressed air supply is turned on before, and shut oi after, the liquid supply.

6. A spray gun comprising a barrel, a discharge nozzle mounted on the forward end of said barrel, said barrel and discharge nozzle having a conjoint bore which along part of its length has a forwardly converging taper, an axially bored jet nozzle mounted in said bore and having its front end disposed rearwardly at a distance from the front end of the tapered part of said bore, said jet nozzle having a stem of less diameter than said bore, whereby to provide a chamber between said jet nozzle and said bore, a liquid conduit for supplying liquid to said chamber, a gas conduit for supplying a compressed gas to said jet nozzle, and a singie valve for controlling the supply both of said liquid to said liquid conduit and of the compressed gas to said gas conduit, said valve comprising a pair of plates, one of which has two pairs of ports therein, one port of one pair of ports conimunicating with said liquid conduit and the other port of said one pair of ports communicating with the source of supply of the liquid, one port of the other pair of ports communicating with said second conduit and the other port of said other pair of ports communicating with the source of supply of the compressed gas, the other of said plates having a pair of grooves therein, one of which registers with and connects both of said one pair of ports when said valve is open and the other of which registers with and connects both of said other pair of ports when said valve is open, said other plate being reciprocably slidable on said one plate and being movable in one direction to open said valve and in the opposite direction to close said valve, the second-named groove of said other plate being longer than the first-named groove thereof, whereby the compressed air supply is turned on before, and shut off after, the liquid supply.

References Cited in the tile of this patent UNITED STATES PATENTS 1,382,64l Heinrich June 28, 1921 1,386,426 Riddle Aug. 2, l92l 1,429,415 Evans Sept. 19, 1922 

